How can I connect to a remote or local database using simple SqlConnection object? I learned to do it this way, but my connection is failing. I read about creation of connection string from this page:
https://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlconnection.connectionstring(v=vs.110).aspx
My code:
using System.Data.SqlClient;
namespace SyncApp_BuiltInProviders
{
public partial class Form1 : Form
{
private void btnSynchronize_Click(object sender, EventArgs e)
{
SqlConnection source_conn = new SqlConnection();
source_conn.ConnectionString ="Server=localhost;Database = ptls; UID = root;Password = ODYSSEY99GRANITE;";
source_conn.Open();
}
}
}
As from your comment in another answer it is clear that you are using the wrong classes. The SqlConnection is a class specialized in connecting to Sql Server/Sql Server Express/LocalDb. It cannot work against a MySql
If you use MySql then you need to download and install the MySql Connector for NET from here.
After that, you need to reference the MySql.Data.dll and add a
using MySql.Data.MySqlClient;
to all the source files that interact with the database.
Finally, all the classes used to work with the database, should be the ones provided by the MySql NET Connector.
They are prefixed with MySql..... (MySqlConnection, MySqlCommand, MySqlDataReader etc.)
If you are used SQL Database, it seems to me that, you have not set username and password. If you have not set username and password then try this.
private void btnSynchronize_Click(object sender, EventArgs e)
{
SqlConnection db_connect= new SqlConnection();
db_connect.ConnectionString ="Server=[your local pc connection name, it is not local host.];Database=[database_name];Trusted_Connection=true";
db_connect.Open();
}
If you use MySql then
private void btnSynchronize_Click(object sender, EventArgs e)
{
//Create a MySQL connection string.
string connectionString="Server=localhost;Database[database_name];Uid=root;Password =your password; ";
MySqlConnection db_connect= new MySqlConnection(connectionString);
db_connect.Open();
}
Finally use following name space
using MySql.Data.MySqlClient;
Related
I am new at this but I have a simple table in my SQL Server with one column name and 2 rows in it. I am trying to show up the names when pressing a button, I need to know how to connect the SQL Server database to the C# code and how to read from a specific table.
namespace WinFormsApp1
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
string connetionString;
SqlConnection cnn;
connetionString = #"Data Source=DESKTOP-REB699D\SQLEXPRESS;Initial Catalog=DBdemo";
cnn = new SqlConnection(connetionString);
cnn.Open();
MessageBox.Show("Connection Open !");
cnn.Close();
}
}
}
But that didn't work, it crashes at the cnn.open(); line of code.
If you are not using any credentials, its windows authentication.
Does adding Integrated Security=True to the connection string help?
Can you login to the DB without credentials on SSMS using Windows authentication option? If so, you don't need user credentials for connecting to DB. If you require a Username and password there,
you either need to include that in the connection string or
you need to enable SQL Server and Windows Authentication option under security tab to access the database without credentials
I'm working on a small project that's unrelated to this, it needs a database to be integrated into it, so I looked into SQLite and tried to teach myself the basics.
My code works fine but I realised if I was to deploy this on another machine it wouldn't be able to connect to the database because it wouldn't have the file as I've hard coded it in (it's running of my C:\ drive currently which will be an issue for users who haven't got it there obviously).
I was wondering if it was possible to update to connection string for the user at runtime? Even say, when the user installs it, it installs a copy of the database and changes its path to that?
Here's my code:
using System;
using System.Windows.Forms;
using System.Data.SQLite;
namespace sqltest
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
string cs = #"Data Source=c:\student.db;Version=3;FailIfMissing=False";
string stm = "SELECT Name FROM Customer";
using var con = new SQLiteConnection(cs);
con.Open();
using var cmd = new SQLiteCommand(stm, con);
using SQLiteDataReader rdr = cmd.ExecuteReader();
while (rdr.Read())
{
MessageBox.Show($"{rdr.GetString(0)}");
}
}
}
}
Thanks for any help!
you can get datasource from config file, e.g. appsetting.json
The connection string that you pass to new SQLiteConnection(...); is actually being passed at runtime already.
Sounds like the simplest solution is to create the database if it doesn't already exists with a predetermined path. This will ensure that when your script runs on a machine that doesn't have a DB, the DB will be created at runtime.
Here's a relevant post: Programmatically create sqlite db if it doesn't exist?
I am a beginner in C # and I intend to create a simple program to check the connection to the mysql server (in this case I am using xampp, so the connection is local).
The problem is that the connection to the mysql server does not work, so the "Can not open connection!" box pops up. I appreciate all the explanations. thank you :)
using System;
using System.Data;
using System.Data.SqlClient;
using System.Windows.Forms;
using MySql.Data.MySqlClient;
namespace WindowsFormsApp1
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void btnSend_Click(object sender, EventArgs e)
{
SqlConnection cnn;
string server = "localhost";
string database = "test";
string uid = "root";
string password = ""; //im using xampp
string connectionString;
connectionString = "SERVER=" + server + ";" + "DATABASE=" +
database + ";" + "UID=" + uid + ";" + "PASSWORD=" + password + ";";
MySqlConnection connection = new MySqlConnection(connectionString);
cnn = new SqlConnection(connectionString);
try
{
cnn.Open();
MessageBox.Show("Connection Open ! ");
cnn.Close();
}
catch (Exception ex)
{
MessageBox.Show("Can not open connection ! ");
}
}
private void button1_Click(object sender, EventArgs e)
{
this.Close();
}
}
}
Thank you for clarifying the specific problem you're having. That's helpful ;)
Thank you, too, for posting the error message.
In the future, please copy/paste the error as TEXT, not an image.
In this case, it would have been nice to run the error text through Google Translate ;)
THE PROBLEM:
Based on the error message, it sounds like your C# program might be trying to use the SQL Server driver to talk to a MySQL database. That won't work :)
SUGGESTION:
Look at any of these links:
MySQL Connector/Net Developer Guide
MySQL C# tutorial
Connect C# to MySQL
At a minimum, you'll also need to get the MySQL driver (e.g. from NuGet):
how to get new mysql connector for c#
I have the same problem after a while i find out i can not use SqlConnection. SqlConnection is for SQL Server i need to install MySql.Data from NuGet:
Install-Package MySql.Data in your Package Manager Console
then i can create MySqlConnection object and connect to your database:
System.Data.IDbConnection cnn = new MySql.Data.MySqlClient.MySqlConnection("my Connection String");
try
{
cnn.Open();
MessageBox.Show("Connection Open ! ");
cnn.Close();
}
Recently we have had an issue with our ERP retrieving some information from our database tables. While this is being fixed I have come up with some work arounds to temporarily, however, they only work because my user has access to the SQL database and can run queries on the database. I would like to distribute an executable program throughout the company (we are relatively small, so I am not worried about bottle-necking my computer) that would allow a different user on another computer to run a query through my computer and retrieve the information to then be output on their computer. This way we don't need to make any changes to users SQL permissions.
How could I possibly do this?
Edit - Additional Info
User A - has permission to query the database on our servers from
their workstation
User B - does not have permission to query the db
User B needs to gather information from a specific db query, yet they don't have access to the db. All that User B needs, is to be returned a string with information from that query.
So not necessarily looking for the remote execution of a program per se, because then how would they get that return value?
I would do it with an application that does something like this.
using MySql.Data.MySqlClient;
namespace WinformFiddle
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
MySqlConnection conn = null;
try
{
conn = new MySqlConnection();
conn.ConnectionString = "server=myserver.mydomain.edu;user id=MyUserWithAccessUsername;password=MyUserWithAccessPassword;persistsecurityinfo=True;database=roomscheduling;Integrated Security=False";
conn.Open();
MySqlCommand selCmd = new MySqlCommand("SELECT ...", conn);
MySqlDataAdapter da = new MySqlDataAdapter(selCmd);
....
This uses MySql, but the exact equivalent can be done with any DB provider. The part of the connection string that says Integrated Security=False tells the system not to use the current user's window credentials but rather what is being provided in the connection string.
The same thing but using Sql Server, I think, would be like this (it's been a while since I use sql server...
using System.Data.SqlClient;
namespace WinformFiddle
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
SqlConnection conn = null;
try
{
conn = new SqlConnection();
conn.ConnectionString = "server=myserver.mydomain.edu;user id=MyUserWithAccessUsername;password=MyUserWithAccessPassword;persistsecurityinfo=True;database=roomscheduling;Integrated Security=False";
conn.Open();
SqlCommand selCmd = new SqlCommand("SELECT ...", conn);
SqlDataAdapter da = new SqlDataAdapter(selCmd);
....
I assume based on the quote below - you are creating a program that you will send to user B to use to run the query and return a string.
"that would allow a different user on another computer to run a query through my computer and retrieve the information to then be output on their computer. "
If this is the case - User B doesnt need any data base permissions. You will put your [user A]'s username and password in the connection string of the program you create. So when User B runs this program you gave him, it will use User As permissions to run and return data.
like this:
<add name="myconnection" connectionString="data source=yoursqlserver;initial catalog=yourdataabase;persist security info=True;user id=UserA;password=userAspassword" providerName="System.Data.SqlClient" />
I have a local project where I am trying to input data from an ASP:textbox to a database.
On building I get the following...
"Failed to generate a user instance of SQL Server. Only an integrated connection can generate a user instance. The connection will be closed."
I'm a little puzzled here, I have checked the database and it is active with the credentials i am trying to connect with.
Here is the code behind
C#
namespace OSQARv0._1
{
public partial class new_questionnaire : System.Web.UI.Page
{
SqlDataAdapter da = new SqlDataAdapter();
SqlConnection sqlcon = new SqlConnection(#"user id=*myuserid*;"+"password=*mypassword*;"+"Data Source=mssql.dev-works.co.uk;User Instance=True;"+"Database=devworks_osqar"+"Trusted_Connection=true;");
protected void Page_Load(object sender, EventArgs e)
{
}
protected void Create_Click(object sender, EventArgs e)
{
DataBinder ds = new DataBinder();
sqlcon.Open();
SqlCommand sqlcmd = new SqlCommand("INSERT INTO QUESTIONNAIRES (QuestionnaireName) VALUES ('"+qnrName.Text+"')");
sqlcmd.Parameters.AddWithValue("#Name", qnrName.Text);
sqlcmd.ExecuteNonQuery();
sqlcon.Close();
}
}
}
Any help would be much appreciated.
Edited code behind (read commment below)
C#
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.Sql;
using System.Data.SqlClient;
namespace OSQARv0._1
{
public partial class new_questionnaire : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
private string myConnectionString;
private SqlConnection myConn;
public new_questionnaire()
{
myConn = new SqlConnection();
myConnectionString += "Data Source=mssql.database.co.uk; Initial Catalog=devworks_osqar;User ID=myusername;Password=mypassword";
}
protected void Create_Click(object sender, EventArgs e)
{
//DataBinder ds = new DataBinder();
SqlCommand sqlcmd = new SqlCommand("INSERT INTO QUESTIONNAIRES (QuestionnaireName) VALUES ('"+qnrName.Text+"')");
sqlcmd.CommandType = CommandType.StoredProcedure;
sqlcmd.Parameters.AddWithValue("#Name", qnrName.Text);
insert(sqlcmd);
}
private void insert(SqlCommand myCommand)
{
myConn.Open();
myCommand.ExecuteNonQuery();
myConn.Close();
}
}
}
Fix error "Failed to generate a user instance of SQL Server due to a failure in starting the process for the user instance."
Content from link pasted and altered below in case reference site is removed in the future:
Step 1.
Enabling User Instances on your SQL Server installation
First we are gonna make sure we have enabled User Instances for SQL Server installation.
Go to Query Window in SQL Server Management Studio and type this:
exec sp_configure 'user instances enabled', 1.
Go
Reconfigure
Run this query and then restart the SQL Server.
Step 2.
Deleting old files
Now we need to delete any old User Instances.
Go to your C drive and find and completely DELETE this path (and all files inside):
C:\Documents and Settings\ YOUR_USERNAME \Local Settings\Application Data\Microsoft\Microsoft SQL Server Data\SQLEXPRESS
(Dont forget to replace the bold text in the path with your current username (if you are not sure just go to C:\Documents and Settings\ path to figure it out).
After deleting this dir you can go to Visual Studio, create ASP.NET WebSite and click on your App_Data folder and choose Add New Item and then choose SQL Server Database and it should work!!!